Abstract: Recent discovery of high-concentration electrolyte systems has opened a new avenue toward the high-voltage, safe, and low-cost aqueous rechargeable batteries. However, the need for generally high-cost organic solutes in the high-concentration electrolyte has become another major obstacle. Herein, we revisited all the commonly used low-cost solutes for high-concentration system and discovered that the use of NaClO4 solute effectively results in a wide electrochemical stability window by suppressing water decomposition and induces stable solid-electrolyte interphase (SEI) layer formation without involving the reduction of salt anions. The SEI layer, composed of Na2CO3 and NaO compounds including NaOH, guarantees the excellent electrochemical storage stability of the full-cell composed of Na4Fe3(PO4)2(P2O7) cathode and NaTi2(PO4)3 anode for the extended period of time. This new class of electrolyte systems provides remarkable cycle stability and a coulombic efficiency of ∼99% at 1C for over 200 cycles, which outperforms the state-of-the-art super-concentrated systems based on NaCF3SO3.

Toward a low-cost high-voltage sodium aqueous rechargeable battery

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DOI: 10.1016/j.mattod.2019.02.004